Variable displacement pump



P 6, 1956 R. L. ALLEN 3,270,674

VARIABLE DISPLACEMENT PUMP Original Filed Dec. 19, 195'? S3 Sheets-Sheet 1 INVENTOR.

ROBERT L. ALLEN ATTORNEY.

Sept. 6, 1966 R. ALLEN 3,270,674

VARIABLE DISPLACEMENT PUMP Original Filed Dec. 19, 1957 Sheets-Sheet ROBERT 1.. ALLEN ATTORNEY- Sept. 6, 1966 R. L. ALLEN VARIABLE DISPLACEMENT PUMP Original Filed Dec. 19, 1957 5 SheetsSheet 5 ROBERT L. ALLEN ATTORNEY- United States Patent Ofice 3,270,674 Patented Sept. 6, 1966 3,270,674 VARIABLE DISPLACEMENT PUMP Robert L. Allen, Atlanta, Ga., assignor to Georgia Tech Research Institute, Atlanta, Ga., a corporation of Georgia Continuation of application Ser. No. 703,898, Dec. 19,

1957. This application May 31, 1963, Ser. No. 284,492

2 Claims. (Cl. 103--38) This invention relates to a variable displacement pump, and is particularly concerned with rotary-driven multiplepiston pumps wherein the volumetric output may be readily varied during operation and independently of driven speed.

This application is a continuation of my copending application, Serial No. 703,898, filed December 19, 1957, for Variable Displacement Pump, now abandoned.

It is of course recognized that there are many and various types of rotatably driven piston type pumps. For the most part such pumps are of constant displacement by virtue of the constantly uniform pump piston stroke. Furthermore, it is customary in such pumps to have but a single piston and cylinder, or tandem type multiples thereof, and hence the load imposed from the driving shaft fluctuates between the peak pump stroke load and the return movement of the piston. Such fluctuation of course imposes a spasmodic load, causing chatter, vibration and undue wear. Problems also arise with respect to the effect of an eflicient sealing and/or packing of the cylinder or piston in such pumps.

While the present inventive concept may be widely varied as to structure and design to meet differing requirements, that form of the invention here shown by way of illustration may be generally defined as including a central body and an odd number of radially disposed piston and cylinder units, here shown as three, arranged at equal radial angularity about said central body. It will of course be recognized that an even number of radial piston assemblies may be used. The odd number, however, is preferable as providing harmonic balance. Five pistons have been successfully employed where the pump has been used as a fuel pump for an eight cylinder engine. Coaxially arranged within said body there is provided a rotary drive member which mounts and rotates therewith a radially adjustable slide including a driving stud. For adjusting the radial relation of the slide and drive stud with respect to the center of rotation of said member, a vertically reciprocable thrust control rod is mounted for rotation with, and axial movement with respect to, the rotary drive member. At the lower end of the control rod, means are provided by which the radial disposition of the stud will respond to the vertical position of the thrust control rod. The stud is engaged with a piston operating head mounted for orbital movement in response to like movement of the stud, the radius of such movement being under the control of the thrust control rod. The head is formed with three piston engaging ways, each engaging a radially reciprocating piston mounted in equally angular radial cylinders. Thus as the drive member rotates, the head will move in its orbital path to reciprocate the pistons, the amplitude of such piston movement being determined by the radial setting of the plate stud and head. In the present form of the invention, each of the piston and cylinder units is supplied from a single source, and the outlet for each cylinder is connected so that the three pump units act to pump fluid from such single source to a single outlet. However, it will be understood that the invention is in no way limited to this particular arrangement; and, if desired, each pump may be individually supplied with fluid and each pump may individually deliver fluid.

It is among the general objects of the invention to provide a novel and improved pump of the class described which will be simple in construction, effective and efficient in operation and well designed to meet the demands of economic manufacture.

A further and more specific object of the invention is to provide a multiple-piston, rotary driven pump so constructed and arranged as to provide for uniform distribution of load on the driving shaft thereof.

Another and important object of the present invention is to provide a pump of the class described, the volumetric output of which may be readily varied to meet varying demands for fluid, and in particular a pump in which said variations may be attained without cessation of the pumping operation.

Another important object of the present invention is to provide a novel and improved packing means for sealing the pump, piston and cylinder so as to provide a uniform seal with a minimum of parts and complication of structure.

These and other objects, features and advantages of the present invention will be apparent from consideration of the following specification, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side elevation of one form of the pump of the present invention.

FIG. 2 is a horizontal cross sectional view taken on line 2-2 of FIG. 1.

FIG. 3 is an enlarged detail cross section taken on the line 33 of FIG. 2.

FIG. 4 is a detail horizontal cross section taken on line 4-4 of FIG. 3 with pistons, piston housings and rocker arm removed.

FIG. 5 is an enlarged detail cross section taken on line 5-5 of FIG. 3.

FIGS. 6, 7 and 8 are reduced cross sectional views taken on line 6-6 of FIG. 3 showing successive positions of the piston driving head during operation.

Referring more particularly to the drawings, it will be seen that the pump may include a central, stationary, generally hexagonal, hollow body 10, three alternate spaced surfaces of which are formed with circular recesses 11 each having a central pump piston aperture 12. Internally, the body is formed with a cylindrical operating chamber 13 and a communicating central vertical shaft bore 14. Mounted in each of the individual recesses 11 is a reduced inner end 15 of one of the three generally cylindrical, hollow, radially extending, pump piston housings 16. Each housing defines a central open ended piston bore 17 within which is reciprocatively mounted an elongate pump piston rod 18 of uniform diameter. The inner end 19 of each rod extends into the chamber 13 through its aperture 12. The outer end 20 of each rod 18 constitutes the pumping head of the piston.

Mounted on the outer end 21 of each piston housing 16 there is a pump casing 22 including a central pump cavity 23 in which the pumping head 20 of the piston reciprocates. The cavity 23 is open to the piston by way of a lateral bore 24. Below the cavity 23 and communicating therewith is an enlarged inlet valve chamber 25 having an inlet port 26 controlled by a ball valve 27 normally urged in closed position by spring 28 adapted to seat the ball against the port 26. Below each casing 22 is secured fluid supply block 29 defining a fluid supply duct 30 leading to chamber 25 and communicating with a through fluid supply passage 31. Similarly, above the cavity 23 there is an enlarged outlet valve chamber 32 communicating with the cavity 23. Fluid passage between cavity 23 and chambers 32 is under the control of a ball valve 33 normally urged in seating position against the upward opening of the cavity 23 by spring 34. Above the chamber 32 is mounted a fluid discharge block 35 defining a fluid discharge duct 36 leading to chamber 32 and communicating with a through fluid discharge passage 37. By this arrangement it will be seen that as the piston rods 18 reciprocate within their housings 16, the pumping heads 20 will move inwardly and outwardly of the cavity 23 causing pressure increase upon outward movement, thus forc ing fluid from the cavity 23 past the valve 33 and thence outwardly through passages 36 and 37. On the inward stroke of the piston, the fluid from the passage 31 will be drawn past the valve 27 and into the cavity 23 for expulsion upon the subsequent outer movement of the piston.

The fluid flow arrangement of the pump here illustrated includes a supply tube 40 leading from some suitable fluid source (not shown) and connected with the fluid feed block 29 of a first pump unit, here shown as the lower right hand unit of FIG. 2. Irrespective of the pumping action of the first unit, fluid will flow freely through the passage 31 thereof to a first intercommunication fluid supply tube 41 connected between the blocks 29 of the first and second pump units. Similarly, fluid can flow freely through the block 29 of the second or intermediate unit, regardless of the pumping action of that unit, to pass through a second intercommunication fluid supply tube 42 to the block 29 of the terminal unit, here shown as the right hand unit of FIGURE 2, where the supply line for the pump units terminates. Fluid pumped by the first unit passes through its block 35 to a second unit. Fluid pumped by both the first and second units passes from the block 35 of the second unit through the second intermediate fluid discharge tube 44 between the blocks 35 of the second and third units. From the block 35 of the third unit, the total pumped fluid passes through a final fluid delivery pipe 45. Obviously, if desired, the tubing arrangement may be such as to supply each unit separately and/or to discharge fluid separately from each unit.

An important feature of the invention is the construction and method of packing and lubricating the pistons to insure an optimum seal of the pump cavity, insuring constant accuracy of the increment of fluid supplied by each piston stroke while minimizing friction and wear of the sealing element. These improved advantages are achieved in the present construction by providing an annular and angular counter-bore, recess or rabbet between each casing 22 and its pump piston housing 16, surrounding and opening into the pump piston bore. The counterbore forms a radial, transverse, flat wall and a right angularly related annular wall 51, coaxially encircling the piston head. The outer face 52 of the housing 16 forms a confining, radial, flat wall 53 parallel with the wall 50 to form a rectangular seating recess for a normally round elastic O ring 54. The more conventional types of O ring packing assemblies usually seat the ring in a recess substantially wider than the normal diameter of the O ring. Such a mounting permits a lateral or rolling motion of the O ring in its seat in response to relative axial movement between the sealed elements. Even though the depth of the recess may be quite small and the O ring tightly engaging the inner element, a tendency for such lateral motion will cause distortion and wear, not only precluding long life of sealing effectiveness but also precluding etficient sealing by which volumetric efficiency is insured. In the present construction, the width of the O ring recess is substantially less than the diameter of the ring, so that a conventional O ring of appropriate size when forced into the recess will conform to the flat side walls, thus securely locking the ring against lateral rolling or deformation.

Lubrication of the piston is provided by a slightly enlarged counterbore 56 extending inwardly from the outer end of the piston rod housings to increase the bore 17 for a distance not less than the maximum stroke of the piston and providing a lubrication clearance space out to the O ring 54. Lubricating oil is supplied to the clearance space by lubrication ducts 57 leading from the clearance space to extend in upper and lower parallel relation to the operating chamber 13 of the body 10 from which lubrication is supplied. By this construction it will be seen that while ample lubrication is supplied for the pump rods, the O ring effectively seals the head end of the rods against loss of lubrication to the pump cavity or loss of pumped fluid to the clearance space. The O ring 54 extends radially inwardly from its tight securement in the recess to bear against the head ends of the pistons, while the relative internal diameter of the ring and the external diameter of the rods is such as to compress the internal 0 ring surface to a flat face 58 providing a broad sealing surface.

For reciprocating the pistons to produce the pumping action of the head ends thereof, there is provided within the chamber 13 a bodily rotating driving head 60 movable in an orbital path, the radius of which is determined by the radial setting of the stud 61 of the slide 62 upon which the head is mounted by way of bearings 63. The head 60 is generally hexagonal, having alternate faces located in planes normal to the axes of the three pump units. Parallel with such faces, the head 60 is formed with downwardly facing piston engaging ways 65, each of which slidably receives the upwardly projecting driving flange 66 at the inner end 19 of each piston rod 18. Thus as the head revolves in its orbital path, as driven by the rotation of the plate 62 and stud 61, the pistons will be reciprocated with a 120 difference in phase and with a thrust length determined by the relative radial location of the plate and stud. The plate 62 is slidably mounted in transverse ways 70 of a driving box, the side wall 71 of which depends from the circular flange 72 at the lower end of tubular shaft 73 rotatably mounted in the bore 14 of the body 10. The shaft 73 is adapted to be rotated through gear 74 driven by a companion bevel gear 75 which is mounted on shaft 76, and journaled in the mounting bracket 77 of the pump.

Variations in the radial setting of the head 60 and its stud 61 with respect to the center of rotation of the shaft 73 is provided by a bell crank 80 rotatably mounted on a stud 81 horizontally disposed between the walls 71 and rotatably therewith. The lower arm 82 of the crank 81 engages a recess 83 in the plate 62. The upper, generally horizontal arm 84 of the bell crank engages a recess 85 at the lower end of a vertically reciprocable control rod 86, rotatable with, but slidable within, shaft 73. By this arrangement it will be seen that as the rod 86 moves vertically Within the shaft 73, such vertical movement will be translated into a rocking movement of the crank 80 which in turn will induce transverse movement of the plate 62, thus altering the radial relation of the stud 61 with respect to the center of rotation of the shaft 73.

From the foregoing, it will be seen that when the stud 61 is located at the center of rotation of the shaft 73, and hence the axis of the rod 86, rotation of the shaft will impart no reciprocatory movement to any of the pistons, since the stud will revolve on its center of rotation. However, upon vertical movement of the control rod 86, the bell crank 80 will rock to move the head 60 laterally in the ways 70, and thus radially with respect to the center of rotation of the shaft 73. After such vertical adjustment of the rod 86, rotation of the shaft 73 will provide an orbital path of movement for the stud 61 on a radius corresponding to the adjustment imparted by the rod. Such orbital movement will provide for an effective reciprocation of the pistons, and thus each piston Will be reciprocated with a stroke corresponding to the radial displacement of the stud 61 with respect to the center of rotation of the shaft 63, and equal in length to twice the distance of such radial displacement, to correspondingly vary the volumetric output of the cylinders.

From the foregoing, it will be seen that the present invention provides a novel, simple and improved rotarydriven, multiple-piston, variable displacement pump. It

Will also be seen that the multiple pistons are so arranged as to uniformly disperse the load on the pump drive shaft, and that the displacement may be readily varied, while the pump is in operation, in accurate and faithful response to adjusting means. Furthermore, a more eflicient sealing means is provided in combination with effective lubrication of the pistons. \iVhile structural details here presented provide one form of the invention, it will be understood that in the practice thereof numerous changes, modifications, and the full use of equivalents may be resorted to without departure from the spirit or scope of the invention as defined in the appended claims.

What is claimed as invention is:

1. A variable-displacement metering pump including a hollow body defining an operating chamber containing a lubricant, a central rotary power shaft, :1 piston driving head in said chamber for rotation by said shaft, driving means movably mounted with respect to said head and transversely displacable with respect thereto to be moved in an orbital path of varying radius in response to rotation of said shaft, a pump piston housing mounted on said body and defining an open ended piston bore communicating at its inner end with said operating chamber, a pump casing mounted on said housing and defining a pump cavity, a piston mounted for reciprocation in said piston bore and having a pumping head extending into said pump cavity, means for reciprocating said piston commensurate with the orbital movement of said driving means and responsive to the radius of such movement, together with means to transversely displace said head during rotation of said shaft, said pump piston housing being counterbored from its outer end inwardly for a distance at least as great as the maximum stroke of the piston and providing lubrication clearance space between the piston and the pump piston housing, intercommunieating means for circulating lubricant from said operating chamber to said piston at said clearance space and thence back to said operating chamber, and sealing means about the pumping head of the piston at the juncture of said pump piston housing and said pump casing for sealing the piston and the pumping chamber against the escape of lubricant and pumped fluid along the piston.

2. In a variable-displacement pump of the type having a hollow central body with a central operating chamber for containing lubricant and a piston with a pumping head which is variably reciprocated from said central body, the combination therewith of a pump piston housing mounted on said body and defining an open ended piston bore receiving said piston and communicating at its inner end with said operating chamber, a pump casing mounted on said housing and defining a pump cavity, said pumping head extending into said pump cavity, said pump piston housing being provided with a counterbore from its outer end inwardly for a distance at least as great as the maximum stroke of the piston and providing a lubrication clearance space between said piston and said pump piston housing, intercommunicating means for circulating said lubricant from said operating chamber to said piston at said clearance space and thence back to said operating chamber, and sealing means about the pumping head of said piston at the juncture of said pump piston housing and said pump piston housing and said pump casing for sealing the piston and the pumping chamber against the escape of lubricant and pumped fluid along said piston.

References Cited by the Examiner UNITED STATES PATENTS 1,227,164 5/1917 Manly 103-174 1,239,059 9/1917 Sundh 103-174 1,397,914 11/1921 Augustin 230-203 1,976,151 10/ 1934 Thaheld 103-154 1,982,958 12/ 1934 Kraus 103-38 1,997,985 4/1935 Thaheld 103-38 2,257,854 10/ 1941 Peterson 103-38 2,266,003 12/1941 Clark 103-174 2,544,055 3/1951 Staats 103-174 2,636,349 4/ 1953 Schnell 103-171 2,709,408 5/ 1955 Orshansky 103-174 2,771,845 11/1956 Eagan 103-153 2,795,195 6/1957 Amblard 103-153 2,845,029 7/1958 Gratzmuller 103-153 2,900,839 8/ 1959 Mackintosh 103-38 2,916,998 12/1959 Miller 103-153 2,921,529 1/1960 Bennett 103-38 2,945,451 7/1960 Griswold 103-174 2,969,738 1/ 1961 Ulbing 103-171 FOREIGN PATENTS 449,429 6/ 1948 Canada. 1,033,552 4/ 1953 France.

569,759 6/1945 Great Britain.

577,287 5/1946 Great Britain.

OTHER REFERENCES German application No. P 11,505, Ia 5921, May 1956.

LAURENCE V. EFNER, Primary Examiner. 

1. A VARIABLE-DISPLACEMENT METERING PUMP INCLUDING A HOLLOW BODY DEFINING AN OPERATING CHAMBER CONTAINING A LUBRICANT, A CENTRAL ROTARY POWER SHAFT, A PISTON DRIVING HEAD IN SAID CHAMBER FOR ROTATION BY SAID SHAFT, DRIVING MEANS MOVABLY MOUNTED WITH RESPECT TO SAID HEAD AND TRANSVERSELY DISPLACEABLE WITH RESPECT THERETO TO BE MOVED IN AN ORBITAL PATH OF VARYING RADIUS IN RESPONSE TO ROTATION OF SAID SHAFT, A PUMP PISTON HOUSING MOUNTED ON SAID BODY AND DEFINING AN OPEN ENDED PISTON BORE COMMUNICATING AT ITS INNER END WITH SAID OPERATING CHAMBER, A PUMP CASING MOUNTED ON SAID HOUSING AND DEFINING A PUMP CAVITY, A PISTON MOUNTED FOR RECIPROCATION IN SAID PISTON BORE AND HAVING A PUMPING HEAD EXTENDING INTO SAID PUMP CAVITY, MEANS FOR RECIPROCATING SAID PISTON COMMENSURATE WITH THE ORBITAL MOVEMENT OF SAID DRIVING MEANS AND RESPONSIVE TO THE RADIUS OF SUCH MOVEMENT, TOGETHER WITH MEANS TO TRANSVERSELY DISPLACE SAID HEAD DURING ROTATION OF SAID SHAFT, SAID PUMP PISTON HOUSING BEING COUNTERBOARD FROM ITS OUTER END INWARDLY FOR A DISTANCE AT LEAST AS GREAT AS THE MAXIMUM STROKE OF THE PISTON AND PROVIDING LUBRICATION CLEARANCE SPACE BETWEEN THE PISTON AND THE PUMP PISTON HOUSING, INTERCOMMUNICATING MEANS FOR CIRCULATING LUBRICANT FROM SAID OPERATING CHAMBER TO SAID PISTON AT SAID CLEARANCE SPACE AND THENCE BACK TO SAID OPERATING CHAMBER, AND SEALING MEANS ABOUT THE PUMPING HEAD OF THE PISTON AT THE JUNCTURE OF SAID PUMP PISTON HOUSING AND SAID PUMP CASING FOR SEALING THE PISTON AND THE PUMPING CHAMBER AGAINST THE ESCAPE OF LUBRICANT AND PUMPED FLUID ALONG THE PISTON. 